1. Field of the Invention
This invention relates to a method and apparatus for detecting mistaken insertion of each battery cell in the manufacturing process of a battery having plural battery cells, as in the case of a unit battery.
2. Description of the Related Art
There has so far been used a battery having plural battery cells enclosed in its casing, for example, a unit lead-acid storage battery. The battery cell of this type of the battery is made up of plural positive electrode plates, connected to an positive electrode terminal, and plural negative electrode plates, connected to a negative electrode terminal. These positive electrode plates are flat-plate-shaped and supported by the positive electrode terminal in parallel with one another. Similarly, the negative electrode plates are flat-plate-shaped and supported by the negative electrode terminal in parallel with one another. These positive electrode and negative electrode plates are alternately combined parallel to one another to make up a battery cell. That is, in this battery cell, each positive electrode plate is sandwiched on its both sides by the negative electrode plate with a gap in-between. Similarly, each negative electrode plate is sandwiched on its both sides by the positive electrode plate with a gap in-between. In the gap between the positive electrode and negative electrode plates is arranged a separator formed of an insulating material.
Also, in the above battery cell, the number of the negative electrode plates is larger by one than that of the positive electrode plates. In this battery cell, two of the negative electrode plates are positioned on both outer sides of the battery cell. Each positive electrode plate in the battery cell is positioned inwardly of both outermost negative electrode plates.
The respective battery cells are enclosed in the casing and, in this state, are connected in series with one another via connector. That is, the negative electrode terminal of the first battery cell is connected to an positive electrode terminal of the second battery cell, a negative electrode terminal of the second battery cell is connected to an positive electrode terminal of the third battery cell and so forth so that respective negative electrode terminals are sequentially connected to the positive electrode terminals. The positive electrode terminal of the first battery cell and the negative electrode terminal of the last battery cell are connected to a positive electrode and a negative electrode of the entire battery, respectively.
Within the casing is charged an electrolytic solution, such as dilute sulfuric acid. This electrolytic solution is intruded into the space between the respective electrode plates for immersing the electrode plates therein.
In the manufacturing process for this battery, mistaken insertion of each battery cell into the casing poses a problem. This mistaken insertion is such insertion in which one or more of the battery cells is inserted in an inverted direction into the casing. If the electrode terminals of the respective battery cells are interconnected in such case in a usual fashion, the positive electrode plates and the negative electrode plates are interchanged in their positions insofar as the battery cells inserted in the inverted direction are concerned, so that optimum charging/discharging characteristics cannot be produced.
There has so far been proposed a battery cell inspection device for detecting this inverted insertion of the battery cells in the manufacturing process for the aforementioned type battery. In this battery cell inspection device, a low-frequency ac voltage is applied across one of the electrode terminals of one of the battery cells and the electromotive force across the opposite side battery cell is measured and compared to a reference magnitude of the electromotive force to check whether or not this battery cell has not be inserted in an inverted position.
In the above-described battery cell inspection device, there is produced only a small difference between a measured value in the correctly inserted battery cell and the incorrectly inserted battery cell to render it difficult to decipher whether the battery cell is inserted in the correct position or in the inverted position. The results of decision in such case tend to be unstable.
Also, if, in this battery cell inspection device, the electrode plate has only a small area, or the number of the battery cells making up a sole battery cell is limited, it becomes more difficult to decipher whether or not the battery cell has or has not been inserted incorrectly to render it impossible to obtain accurate results.